An airplane is flying at 35000 feet above sea level. The airplane starts to descend at a rate of 2500 feet per minute. Let m be the number of minutes. Which of the following expression describe the height of the airplane after any given number of minutes?

In this case, the airplane is flying at 35000 feet and descend 2500 feet every minute. That means the airplane descend rate is 2500 feet/min. Since the duration is m minute then you need to multiply it by the descending rate. Then the formula that can count the airplane height would be:

Airplane height:

35000feet - (2500feet/min x m min)

35000feet - 2500m feet